This invention relates to a nuclear fuel element for use in light water moderated nuclear reactors, heavy water-moderated nuclear reactors, etc. and a process for fabricating the same, and particularly to a nuclear fuel element suitable for plutonium-containing nuclear fuel and a process for fabricating the same.
A nuclear fuel element for use in a light water-moderated nuclear reactor or a heavy water-moderated nuclear reactor comprises fuel pellets, a thermal insulator, a plenum spring, etc. filled in a cladding, both ends of the cladding being sealed with end plugs by welding. In such a fuel element is normally a helium atmosphere, and such a fuel element is fabricated by firstly welding a lower end plug to a cladding, filling a large number of fuel pellets and a thermal insulator in the cladding, then vacuum-degassing and drying the inside of the cladding in a temperature range of 300.degree.-400.degree. C. to remove moisture from the fuel pellets and the cladding, inserting a plenum spring into the cladding, and finally welding an upper end plug to the cladding in a helium atmosphere, thereby sealing the cladding.
Nuclear fuel elements with fuel pellets containing plutonium obtained by reprocessing fuel used in a light water-moderated nuclear reactor have been fabricated. Plutonium has a high hazardness, and a sufficient safety control is required for fabricating the nuclear fuel elements.